Nick Clegg is planning to introduce all-women shortlists for the Liberal Democrats if not enough female candidates are selected in winnable seats in 2015.
The radical policy change, which will upset many activists who believe it would go against the party's constitution, would be introduced in the next Parliament as many candidates have already been selected for the election in 18 months' time.
Only 12 per cent of Lib Dem MPs are women, and there are none at all from ethnic minorities. Lib Dem sources said a number of "excellent" female and ethnic minority candidates have already been selected to replace outgoing Lib Dem MPs and in winnable seats for 2015. But if the female tally does not increase dramatically, all-women shortlists will be imposed for the 2020 election.
The policy change emerged as Labour highlighted figures showing how David Cameron and Mr Clegg have failed to display equality when picking out their MPs for honours.
Mr Cameron awarded knighthoods to two Tory MPs sacked as whips in the reshuffle, meaning he has now awarded honours to nine male MPs. Only one woman, Angela Watkinson, has received a damehood.
The Deputy Prime Minister has not awarded any women MPs damehoods, but four male Lib Dem MPs have been knighted since the election, and there are now seven Lib Dem knights – the same as the number of the party's women MPs.
Of the six Labour MPs honoured since the election, four have been women.
Labour's Equalities spokeswoman, Gloria de Piero, said: "David Cameron's problem with women shapes Conservative policy and personnel. Sacked men seem to get rewarded whereas sacked women get ignored. It is essential in modern politics that those at the top table reflect modern Britain. That goes for gender as it does race and class."