Burkhard Lischka, who sits on the Bundestag’s intelligence oversight committee, said: “If it proves to be true that the American president passed on internal intelligence matters that would be highly worrying.”
Noting that Mr Trump has access to “exclusive and highly sensitive information including in the area of combating terrorism” the Social Democratic Party (SDP) politician said that if the President “passes this information to other governments at will, then Trump becomes a security risk for the entire western world”.
Mr Lischka’s party is part of Germany’s governing coalition led by Angela Merkel’s conservatives.
The Chancellor visited the White House in March, where Mr Trump – already a hugely unpopular figure in Germany – appeared to refuse to shake her hand during an awkward joint press conference.
Counter-terror operations were among the issues discussed by the two leaders, with Germany standing as Nato and intelligence partner.
Having led Germany under three presidents, Ms Merkel has also negotiated extensively with Vladimir Putin, who is expected to meet Mr Trump for the first time at July’s G20 summit hosted by the German Chancellor in Hamburg.
Allegations that the President passed Russian officials classified intelligence on Isis threats relating to a widening laptop ban on passenger aircraft have threatened to damage the US’ relationship with allies.
The information reportedly shared in last week’s closed-door meeting with Russian foreign minister Sergey Lavrov and ambassador Sergey Kislyak is said to have been received under an intelligence sharing agreement with Israel.
The scandal comes days before Mr Trump visits the country on his first foreign trip, with the Israeli ambassador to the US, Ron Dermer, saying it has “full confidence in our intelligence sharing relationship with the United States”.
The claims have sparked condemnation by both Republicans and Democrats following a series of apparently contradictory statements from the White House and Mr Trump.
Hours after top officials claimed the original Washington Post report on disclosures was “false”, the President tweeted that he had the “absolute right” to share “facts pertaining to terrorism and airline flight safety” with Russia. The information appears to be related to the basis for a ban imposed by the US and UK in March on laptops and tablets from being taken in hand luggage from 10 airports in Muslim-majority countries, which could be expanded to Europe.
Aides have maintained that no “inappropriate” information was shared but repeatedly failed to deny the intelligence passed on was classified.
HR McMaster, the national security adviser, claimed the real threat to national security was leakers ”releasing information to the press”.
In an off-camera briefing, White House press secretary Sean Spicer repeatedly refused to comment on specific allegations but at one point appeared to confirm intelligence was passed on.
When a journalist asked whether the US had reached out to the ally that provided the information, he replied: “I’m not going to comment on specifically where it came from.”
He added: “My understanding is the President, of course, has classification authority…so the President can always discuss common threats or common issues with other heads of government or other government officials as he deems appropriate to tackle the threats our country faces.”
Before disclosing intelligence to another country, there would normally be an evaluation of costs and benefits, close consultation with American agencies and detailed consideration of how to mitigate risks.
The US has several intelligence-sharing agreements with allies, including the Five Eyes programme with Britain, Canada, Australia and New Zealand.
The fact the information reportedly went to Russia during investigations into alleged links between Mr Trump’s campaign team and the Kremlin has generated alarm, as well as Moscow’s ties with Iran, China and the Syrian government.
John McCain, the Republican former presidential candidate and Senate Armed Services Committee chairman said the reports were ”deeply disturbing“.
He said the claims sent a “troubling signal” to American partners around the world, and that if the information was shared without an ally’s knowledge, other countries could be from sharing intelligence in the future.
“Regrettably, the time President Trump spent sharing sensitive information with the Russians was time he did not spend focusing on Russia’s aggressive behaviour, including its interference in American and European elections, its illegal invasion of Ukraine and annexation of Crimea, its other destabilising activities across Europe, and the slaughter of innocent civilians and targeting of hospitals in Syria,” Mr McCain added.
Steny Hoyer, one of the most senior Democrats in the House of Representatives, said Mr Trump’s presidency was “dangerous” and the claims were the latest example a White House riven by incompetence, chaos and conflicts of interest.
“I think there is an erosion of confidence among the American people and an erosion of confidence of the international community,” he added.
Mr Hoyer added that it was too early to consider impeachment proceedings against Mr Trump, but that “it is time for Republicans to say, ‘enough’”.