Brexit-backing MPs and ministers have been condemned as "disgraceful" for refusing to guarantee the rights of EU citizens in the UK as it emerged almost 200 people working in Parliament face an uncertain future because of their nationality.
Liberal Democrat leader Tim Farron said the Government was happy for parliamentary staff to be used as "bargaining chips" in negotiations with Brussels.
Theresa May has said she wants the rights of EU citizens in the UK, and Britons on the continent, to be resolved early in the Brexit negotiations.
But the Prime Minister has resisted pressure to unilaterally offer guarantees to EU citizens, preferring to ensure reciprocal agreements are reached for the Britons living in other member states.
Figures obtained through Freedom of Information requests by Lib Dem London Assembly member Caroline Pidgeon revealed the numbers of parliamentary staff whose status could be affected by Brexit.
There are some 195 EU nationals working in the Commons and Lords, including 35 Irish citizens whose "special status" the Government has vowed to maintain.
A further 16 hold EU-non EU dual nationality status and could potentially be affected.
Mr Farron said: "MPs who voted for Brexit seem happy to have doors opened for them and be waited on in restaurants in the Palace of Westminster by EU staff, yet they are effectively saying to staff 'you might have worked here all your adult life, but at any given moment we might send you packing if we are unable to use you as bargaining chips'.
"That is disgraceful.
"The Government should guarantee the right to remain of all EU citizens and give the people a final say on the Brexit terms. You can't have a hard Brexit and a fair deal for EU workers."
Ms Pidgeon said it was "simply hypocritical for any MP to vote against EU citizens being guaranteed the right to remain in the UK, and then spend the rest of the evening in a Commons' bar staffed by EU citizens".
Meanwhile, Ireland's ambassador to the UK Daniel Mulhall said he felt "sadness and regret" about Brexit, which marks a "new and uncertain chapter in Irish-UK relations".
In a blog post he said: "I accept, of course, that a decision has been made by a referendum. As an independent country, the UK is fully entitled to leave the EU.
"Ireland and our remaining EU partners must seek to make the best of this new situation, however regrettable it might seem to us."
He added: "It is, in my view, unfortunate that the UK is set to unravel itself from more than 40 years of economic and political interaction with its fellow European nations, which has created such a positive legacy of peace and prosperity.
"We hope that this will ultimately work out well for the UK and the EU, but there is no doubt that this will demand some skilled negotiating and a will to seek compromise solutions if we are to reconcile our respective sets of interests and aspirations."
A Government spokesman said: "EU nationals make a vital contribution to our economy and our society, and that's why we want to reach an early agreement on the rights of UK nationals in the EU and EU nationals in the UK.
"We welcome the fact that our European partners are also prioritising this and will be seeking the earliest possible agreement on this issue."