Parents of missing Madeleine join victims of tabloid excess and libel reformers in open letter to David Cameron  

Kate and Gerry McCann, the couple whose daughter Madeleine went missing in Portugal, have written to the prime minister urging him to abandon his government's plans to alter no-win, no-fee legal agreements.

The couple, making their first public intervention in politics, are among a group of libel reform campaigners and well-known victims of tabloid newspapers who warn that plans to rewrite what are known as conditional fee agreements (CFAs) will ensure that only the rich have access to justice in future.

The letter, to be delivered to David Cameron on Monday, comes before Tuesday's third reading in the House of Lords of the legal aid, sentencing and punishment of offenders bill (Laspo), which has already suffered nine defeats on different amendments at the hands of peers.

The letter is also signed by Christopher Jefferies, who won libel damages from eight newspapers over false allegations during the Joanna Yeates murder inquiry in Bristol, and a consultant cardiologist who had to defend himself against libel claims when he criticised medical research.

It is the first time the McCanns have voiced their concerns about the impact of the government's legal reforms.

The letter has been co-ordinated by Hacked Off, which campaigned for a public inquiry into phone hacking, and the Libel Reform Campaign.

As well as cutting £350m out of the Ministry of Justice's annual legal aid budget, the Laspo bill will reconfigure no-win, no fee agreements. It prevents claimants from recovering their expensive insurance premiums and lawyers' success fees from losing defendants. Instead, the costs will have to be paid out of any final award.

Martin Moore, of Hacked Off, said: "The government suggest they are going to deal with costs reform for privacy and libel cases in the forthcoming defamation bill, because they accept there is a problem. In that case they need to remove these sorts of cases from the scope of the current legal aid bill. That would also mean that the Leveson Inquiry can then be allowed to look at this issue as well without having been pre-empted by the government."

The justice secretary, Kenneth Clarke, has condemned the current system of CFAs for encouraging a "compensation culture" under which claimants sue too readily without thinking much about the costs incurred. Those with good causes will always find lawyers to take on their cases, it is argued.

Opponents of the changes, such as the Law Society, which represents solicitors, warn that it will make it unattractive for lawyers to take up cases and will stop the less well-off from obtaining redress through the courts. The letter to the prime minister warns: "Parliament is on the cusp of passing a law that will grossly restrict access to justice for ordinary people in privacy and libel cases, without even any saving to the public purse. We strongly object to the passing of this unjust measure and urge you to amend it before it is too late.

"A successful libel defendant obviously does not get any damages so these reforms will prevent all but the rich from being able to defend their right to free speech against wealthy or corporate libel claimants.

"In future ordinary defendants, like Peter Wilmshurst, Hardeep Singh and Heather Brooke, will also be unable to get support for legal action taken against them often by large institutions with deep pockets trying to silence them. That would be bad news for science and medicine, for free religious debate and for transparency in the public interest.

"And victims of the tabloid press like Christopher Jefferies, Bob and Sally Dowler, Kate and Gerry McCann and Robert Murat will not be able to take legal action against the tabloids for hacking into their phones, for false accusations, and for gross misrepresentation."

Kate and Gerry McCann accepted damages of £550,000 and a high court apology from Express Newspapers over "utterly false and defamatory" stories published about the disappearance of their daughter in 2007. The letter argues that newspaper corporations with big legal departments will be able to intimidate victims of false stories because they would face millions of pounds in costs if they lose.

Wilmshurst, one of the signatories, is a consultant cardiologist who used a CFA to successfully defend himself in three libel actions brought by an American company. He said: "The government say they expect people to pay lawyers' success fees from their damages. But defendants in libel actions don't win damages, they only win their free speech rights.

"These reforms obviously don't work for innocent libel defendants and I am shocked the government has not yet listened to our plight. If this bill becomes law in its current state, people like me will not only have to risk their house for the other side's costs, but would not be able to find a lawyer. It is a terrible attack on free expression of doctors and scientists."

Dr Simon Singh, of the Libel Reform Campaign, said: "Although I did not wholly rely on a no-win, no-fee agreement when I successfully defended myself against the British Chiropractic Association, scientists, doctors and writers like me nearly always need some help in financing a defence against a wealthy libel claimant. Without proper provision, we will be unable to defend our freedom of expression. I know the government understands the importance of reforming libel law to make it fairer for all, so I am optimistic the problem will be solved."

Last year the parents of the murdered teenager Milly Dowler also wrote to Cameron asking him to reconsider the bill urging him to abandon legal reforms that will prevent victims suing for compensation. A Downing Street spokesman said on that occasion: "The government is absolutely committed to ensuring that people can access the justice system regardless of their financial situation, which is why we are committed to maintaining 'no win, no fee' arrangements.

"There are many deserving cases brought before the courts. But we have to stop the abuse of the system by others pursing excessive, costly and unnecessary cases. Under the current arrangements, innocent defendants can face enormous costs, which can discourage them from fighting cases. This simply isn't fair.

"By balancing the costs more fairly between the claimant and defendant, these changes will ensure that claimants will still be able to bring deserving claims, and receive damages where they are due, and most importantly they will make the no win, no fee system sustainable for the future.

"So in order to ensure that the no win, no fee cases continue to provide fair access to justice for all, we have to make changes."

The Dowlers' lawyer, Mark Lewis, said: "The reply we got from David Cameron simply said that their sort of high-profile case would always be able to get legal help, but said nothing about how they could protect themselves from Mr Murdoch's costs if they had lost, given the abolition of the insurance arrangements. And anyway, why should only so-called high-profile cases have access to justice? The law should not pick and choose in that way."