Foreign Secretary Robin Cook has refused to hand over to a Commons committee key documents in the arms-to-Africa row.

In a bluntly-worded letter to the foreign affairs select committee, he risked accusations of contempt of parliament by insisting the documents could not be released because they would prejudice the independent inquiry into the affair.

His letter was published as Foreign Office minister Baroness Symons told the Lords she had not misled them over the issue.

She told peers she had deliberately not informed them of a previous Customs inquiry into the issue because that would have risked tipping off those under investigation.

The two responses will ensure that the sanctions-busting allegations continue to harry the government and could lead to a head-on clash with the powerful Commons committee.

Only last week senior foreign office official Sir John Kerr was threatened with contempt of parliament for refusing to reveal documents about the alleged selling of arms in Sierra Leone by the firm Sandline International.

Prejudice investigation

And, in angry exchanges, he was given until the end of last week to answer the committee's questions.

But in a letter to committee chairman Donald Anderson today, Mr Cook insists: "The government cannot disclose information which falls within the remit of Sir Thomas Legg's investigation while it is in progress because to do so could prejudice it."

"It is also Sir Thomas Legg's view that the release of documents now could be damaging to the prospects for the early completion of a comprehensive and consistent report.

"As you said in the Commons, it would be unwise for your committee to attempt to duplicate a parallel inquiry."

"The Government will not withhold information for longer than is necessary to ensure that the full and independent investigation which I have established can complete its work without prejudice.

"However, we cannot, before the completion of Sir Thomas Legg's report, release or discuss the documents before it, including those sought by members of the Committee."

Peers not misled

Meanwhile, in the Lords, Lady Symons also hit back at suggestions she had misled peers by failing to tell them what she knew of the Customs inquiry into Sandline.

"I did not deliberately mislead this House - I did not do so inadvertently either."

She had been briefed on the probe on March 10 - the same day she addressed the Lords on the issue - but had been briefed to say nothing.

"And quite right. It would have been highly prejudicial and quite wrong to make the referral public at that stage.

"Doing so would have alerted those who were potentially under investigation and would have been unfair to them if the allegations were subsequently found to be groundless."

She added: "The notion that I or others in the Foreign and Commonwealth Office deliberately concealed these things to protect ourselves is particularly absurd, given that it was the Foreign Office itself that passed the accusations to Customs and Excise which led to their investigation.

"If any of my remarks, today or at any other time, are found to be inaccurate, I will correct them," she said.