Four parliamentary committees have criticised the Foreign Office for circumventing its own ethical policy over arms exports to Zimbabwe and Morocco.

MPs said ministers, including foreign secretary Robin Cook, had made a "serious error of judgment" in over the last two years by granting arms export licences to Zimbabwe for military aircraft parts at a time when Zimbabwe was intervening in the Congo.

Their report also attacked the granting of licenses for the refurbishment of 30 artillery guns used by Morocco in the Western Sahara.

Cook had told the committees that the sales had been approved because previous grounds for rejecting the agreements were undermined by a UN ceasefire. In strong parliamentary terms, members dismissed his defence as Whitehall fudging the issue. "It is for UK ministers and not the UN Secretariat to decide on arms export licences," they concluded.

Members also attacked the government for its continuing failure to implement the legislation changes recommended by the Scott report in the wake of the arms-for-Iraq affair.

The Foreign Office accepted that information sent to the committee was sent inaccurate information but disputed that any of the other issues were outside its remit. The government, it claimed, was satisfied that the weapons exported to Zimbabwe would not be used in the conflict.

Foreign Office minister Brian Wilson defended the government saying the department was now more open.

"The government has put in place a huge amount of parliamentary scrutiny. This situation has been confirmed and, indeed, the report recognises that. It acknowledges that the government created an unprecedented degree of transparency producing one of the most accountable systems of arms licensing in any major western arms-supplying country," he said.

Lib Dem foreign affairs spokesman Menzies Campbell expressed his disappointment at the findings.

"I am extremely disappointed that the committee has drawn back from its original comprehensive proposals," he said. "Transparency and accountability are essential for public confidence in arms exports. We are still waiting patiently for the draft bill to bring arms export legislation up to date, recommended by Scott, promised by Labour in opposition and not delivered in four years of government."