Labour was told “months ago” about an alleged spy in the Commons, the shadow foreign secretary has suggested.
David Lammy said the official opposition was often briefed on “things that are of major concern” as part of the Privy Council, which advises the monarch.
His words will heap further pressure on the foreign secretary James Cleverly to set out what he knew and when.
Senior Tories, including the former Tory leader Iain Duncan Smith, have demanded Mr Cleverly come clean - in light of his recent controversial visit to China.
The Commons Speaker Lindsay Hoyle told parliament that “the MPs who needed to be told were told”.
Mr Lammy told Radio 4’s PM programme: “We as the Opposition get routine briefings from the security services... and indeed, on privy council terms we hear about things that are of major concern.
“And this did come to the Opposition as an issue we could be briefed on many months ago, and were briefed on many months ago.”
The foreign secretary was accused of “project kowtow” when he visited China last month, with Mr Duncan Smith saying it “smells of appeasement”.
Now MPs want to know if the trip was planned in the knowledge an alleged spy had infiltrated the heart of Westminster.
During a statement in the Commons, Sir Iain asked: "When did the Foreign Secretary get told about this investigation? Was it before he went to Beijing, and if he went to Beijing with this knowledge, did he raise it with his counterpart in Beijing, because it's very important to know whether we have already said it.”
Deputy prime minister Oliver Dowden said the government did not provide a "running commentary" on intelligence matters, adding that Mr Cleverly "regularly raises electoral interference and interference with our democratic institutions" with his Chinese counterpart.
Mr Duncan Smith and a number of other senior Tories including the security minister Tom Tugenhadt were sanctioned by China two years ago.
Labour said it did not comment on briefings under Privy Council rules.
