A coordinated push to protect whistleblowers, journalists and victims of sexual assault from being sued by those who wish to silence them has been launched in both houses of parliament.

Two private members’ bills designed to crack down on strategic lawsuits against public participation, known as Slapps, have been introduced by Conservative members within 24 hours of each other, and are likely to attract cross-party support.

Labour ministers are understood to be supportive of the bills after frustration in the Ministry of Justice that similar measures did not form part of the king’s speech.

However, sources said progress was at an early stage given the political turmoil about a potential leadership challenge to Keir Starmer – though the MoJ would offer advice on the drafting.

The bills follow a long campaign for better protection from financially crippling lawsuits for those speaking up on issues of public interest. Claims that go all the way to trial can cost as much as £1m a party in legal fees, with the losing party paying the other side’s costs.

Tina Stowell, a former BBC communications chief who was leader of the house of Lords under David Cameron, published a draft bill on Tuesday, followed by John Whittingdale, the MP for Maldon and former Conservative culture secretary, who presented his strategic litigation against public participation bill on Wednesday.

Whittingdale said his bill, which is set to be debated in November, had support “across parliament” and from “all sections of the media”. He said Slapps “represent an abuse of the legal system and for too long have been used by the rich and powerful to suppress legitimate investigative journalism and to muzzle free expression”.

Lady Stowell said: “The attack on free speech represented by Slapps is a stain on our legal system and a threat to a functioning democracy. For too long British courts have been used to hush up unethical behaviour and corporate abuses.”

Her draft bill allows defendants facing libel suits, and other forms of legal action, to ask a judge to dismiss the case early in the process, before costs rack up, if they can show that it relates to a matter of public interest.

Defendants whose cases are dismissed can also be awarded costs, and the court can impose penalties on claimants who deliberately prolong the process or cause delays.

Susan Coughtrie, a co-chair of the UK Anti-Slapps Coalition, said: “Now we have the opportunity to turn this support into robust, accessible and universal protections for everyone, ensuring justice is available to all, not just those who can afford it.

“Left unaddressed, Slapps allow bad-faith actors to control and restrict the information available to the public, impacting our knowledge of the world around us. As a result, protections, such as those announced this week, not only protect the person speaking out but the public interest information that sustains democracy.”

The Guardian and other media have highlighted how the wealthy and powerful, from oligarchs to corporations, have used the threat of legal action to silence those with fewer resources. In a number of high-profile cases, women reporting rape and sexual abuse have also been dragged to court after speaking out.

Both Conservative and Labour leaders have supported reform. In 2023, the Conservatives introduced limited protections for those speaking up on economic crimes, such as money laundering. But the legislation does not help those raising issues related to human rights, for example.

In October 2024 Keir Starmer promised action, describing abuse of courts by the rich and powerful as “intolerable”, but the government has yet to bring forward any legislation of its own.

Other countries already have anti-Slapp laws. In many states in the US, judges have broad powers to dismiss abusive cases. In the EU, a directive was introduced in 2024 but member states have been slow to bring it into law.

The new EU law is limited in that it excludes criminal matters. However, it does allow EU citizens being sued abroad to challenge those targeting them in EU courts. Greenpeace has already put this provision to the test in the Netherlands, in a case involving a US oil pipeline company.