Nearly half of English farmers have yet to receive EU subsidies for last year, as the government faces more criticism over a new system of payment.
A new system of payment was agreed last year
As the deadline nears for farmers to fill in this year's claim, many say they and other rural businesses are suffering because of the delays.
Administering the new system is complicated and IT costs have doubled.
Last month former Environment Secretary Margaret Beckett said she recognised the delays caused a "human crisis".
The Commons Environment, Food and Rural Affairs Committee is trying to find out why the money still hasn't been paid, months after the original deadline.
A new system of payment was agreed last year, which provides farmers in England with an annual cheque, rather than separate subsidies on individual sales.
Each farm's subsidy is calculated according to past receipts and land area.
BBC rural affairs correspondent Tom Heap said the late payment had so far cost farmers about £20m in interest.
The shortfall also hurts other rural businesses in the supply chain, and critics claim the government owes "the countryside" nearly £1 billion, our correspondent said.
The Commons Environment, Food and Rural Affairs Committee (Efra) launched an inquiry into the new scheme in October over concerns the March deadline would be missed.
In last week's Cabinet re-shuffle Margaret Beckett was given the post of Foreign Secretary, while David Miliband took on the job of environment, food and rural affairs.
Critics have urged the new Defra team to sort out the problems as soon as possible.