By Ian Dunt Follow @IanDunt
Coalition policies would have prevented the Dowlers pursuing News International, the family has said.
In a major political intervention, the family, who recently won a multi-million pound payment from the media group, said they would not have been able to pursue the case if cuts to legal aid and the 'no-win-no-fee' system had already gone through.
"We are sure you do not want to go down as the prime minister who took the rights away from ordinary people so that large companies could print whatever they like and break the law," the family wrote in a letter to David Cameron and Nick Clegg.
"We were lucky that we fell under [the current] system. We understand that the new law affects thousands of people who want to sue News of the World and other newspapers."
Reforms currently being pushed through by justice minister Jonathan Djanogly would make 'no-win-no-fee' arrangements much harder to secure.
Supporters say the reform will clamp down on the increasingly litigious culture in Britain. Opponents argue the move leaves ordinary families at the mercy of large corporations and insurance companies in cases of negligence, accidents and fraud.
"After all they have been through we welcome - and are humbled by - the intervention of the Dowler family in this debate," commented Des Hudson, chief executive of the Law Society.
"They have succeeded in making it clear to the prime minister that it is ordinary families with terrible life challenges that will be impacted the most. They will be the losers."
Campaigners say the combination of the 'no-win-no-fee' reform with a £350 million cut to legal aid leaves victims with little support when they become entangled in legal disputes with corporations.