Political correspondent, BBC News
Carers should be entitled to more benefits, a union says
The government is coming under pressure to give bigger incentives to encourage Britain's 6m carers to go out to work.
Full-time carers earning below £95 a week can claim the carers' allowance of £50.55 but higher earners get nothing.
Shop workers' union Usdaw says this is a "disincentive" for those who want to work. It wants a higher allowance and for the earnings limit to be tapered.
Ministers says they are committed to reviewing support for carers as part of their longer term welfare reform plans.
Usdaw general secretary John Hannett said: "It really needs improving. There's a disincentive to increase hours - there are many Usdaw members and other carers who want to work extra hours."
The union is pushing ministers to introduce a taper on earnings, so that carers earning up to £245 a week can still claim some allowance.
Mr Hannett said: "What we're trying to do is work in a way that values carers, allows them to work extra hours where they can, also act as an incentive to go to work and balance their caring with going to work."
The government has said it will reform the allowance, but there is no fixed timescale for a review.
A Department for Work and Pensions spokesman said: "The government is committed to reviewing the financial support for carers as part of the longer-term welfare reform programme."
But the charity Carers UK said the allowance was "outdated" and the rules were "unfair and a disincentive to work".
Unions are pressing Labour to commit to several changes at the party's national policy forum later this month.
There have been indications from ministers that they are sympathetic to some family-friendly proposals like allowing parents the right to take leave if their child is ill.
But Labour will be under close scrutiny over whether they accept any demands, as unions currently provide more than 90% of the party's funding.