Political parties are to be forced to declare how many women, ethnic minority and disabled applicants they reject as potential parliamentary candidates under cross-party plans backed by Commons Speaker John Bercow.
The Speaker's Conference, tasked by Prime Minister Gordon Brown to investigate the lack of diversity in Parliament, said today that transparency about the people putting themselves forward as would-be MPs was essential.
The main party leaders have already agreed to publish updates on the outcomes of their candidate selection processes.
But the Speaker's Conference insisted that greater detail about who had applied - and failed - to become candidates was also necessary to exert pressure on the parties.
"To monitor progress properly requires data from all stages of the selection process, from the initial call for applicants to the final outcome," it said in its report.
"Otherwise we will only ever know about the individuals who are successful."
The Conference, which is chaired by Mr Bercow, said it would table an amendment to the Equality Bill requiring the information to be declared in six-monthly reports by each of the parties.
In its report, it said that the parties were "effectively the gatekeepers to the House of Commons" but said their attempts to increase diversity had been "uneven".
There is concern, echoed by the party leaders themselves, that the Commons is not representative enough of people who are not white, middle-class, middle-aged and able-bodied.
Anne Begg, the vice-chairman of the Conference, said: "Unless the performance of the different parties can be compared with each other, or with the performance of parties throughout the world, there is likely to be insufficient pressure for the political parties to pursue the cultural change which is needed from them before we can have a House of Commons fit for the 21st century."