Former Environment Secretary Margaret Beckett should be called to account over the "fiasco" of delayed EU payments to farmers, MPs have said.
Farmers say the delays caused major hardships
The Environment, Food and Rural Affairs Committee called the handling of the new Single Payments Scheme an "embarrassing failure".
In a report, it complained Mrs Beckett and senior officials had not been held "personally accountable" for delays.
But a spokesman for Mrs Beckett said she took decisions "in good faith".
The committee said problems could cost the government up to £500m.
Last month, it was revealed that UK taxpayers could face a £300m European Commission fine for the delays.
The environment department, Defra, said it was still negotiating the exact amount.
A computer problem at the Rural Payments Agency (RPA), set up to deal with EU subsidies, had caused delays in payments to thousands of farmers, it added.
The committee's chairman, Conservative MP Michael Jack, said: "The reason that we are calling for people to consider their positions is because of Defra's failure to carry out one of its principal core functions."
He added: "Those involved should examine their consciences about the role they played in this failed venture, which could well cost Defra and farmers up to half a billion pounds."
Peter Kendall, president of the National Farmers' Union, said: "The RPA may still be limping, but it is showing some signs of improvement.
"It is truly terrible. This saga has cost farmers about £20m of their money and untold stress.
"We don't know yet what it will cost Defra in fines."
The committee questions why some leading Defra and RPA officials most closely involved with the scheme have stayed in post or moved on unscathed.
Its report mentions Mrs Beckett (now the foreign secretary), former permanent secretary Sir Brian Bender and the director general for sustainable farming, food and fisheries, Andy Lebrecht.
The MPs' report said: "A culture where ministers and senior officials can preside over failure of this magnitude and not be held personally accountable creates a serious risk of further failures in public service delivery."
The committee wants new guidance to make clear to ministers what they should do to take responsibility in the event of serious departmental failure.
It also recommends that the Cabinet secretary reappraises the work of the past and present members of Defra's senior management team to determine whether they should remain in post.
A spokesman for Mrs Beckett said: "The foreign secretary is, of course, currently dealing with the Iranian situation and is working for the safe return of our personnel."
He added: "As secretary of state at Defra, she took decisions in good faith on the Single Farm Payment based on the information and expert advice given to her at the time."