The government has published new regulations making clear that the carer's allowance earnings limit will increase by just £2 a week from May 20.
The earnings limit is a rule that prevents a carer from receiving carer's allowance if their earnings, after certain deductions, are more than £100 per week.
From May 20 this figure will increase to £102 per week.
Derek Sinclair, Welfare Rights Adviser at Contact a Family said: "Whilst any increase in the earnings limit is to be welcomed, we are disappointed that the increase will not be greater, especially since the figure has been frozen at £100 per week since 2010."
"A parent who works 16 hours on the national minimum wage may find they are earning too much to get carer's allowance once the national minimum wage increases from October 2014.
"As a result some of these parents will face a choice of either losing carer's allowance or cutting their hours and losing working tax credit.
"Parents who think their earnings will be slightly too high should contact our free helpline - 0808 808 3555 - to discuss whether they have childcare costs or pension contributions that can be deducted from their earnings in order to help them qualify for carer's allowance."
For more information go to the Contact a Family website