British diplomats will not deal with French far-right politician Marine Le Pen even if she becomes the country's next president under current rules, MPs have been told.
Long-standing protocols mean UK officials shun the Front National and her team, the new ambassador to Paris said.
Lord Llewellyn of Steep told the Foreign Affairs Committee that his staff are making contacts with other key contenders in the presidential election.
But "there is a policy of not engaging" with the Front National party, he said.
Asked what would happen if Ms Le Pen wins, he told the committee: "That is the policy that has been the policy for many years.
"The policy is a matter for ministers."
MPs were also told Britain must not hang its Brexit negotiation hopes on winning over German chancellor Angela Merkel.
Lord Hill, the UK's former European commissioner, said wartime hang-ups mean Germany is "frightened" of being in charge.
The peer insisted the renegotiation carried out by David Cameron ahead of the EU referendum "was the best deal" that could have been secured.
Germans describe Britain as "always wanting extra wurst" and "they do think we have had extra wurst", he told the committee.
"My advice would be that putting all your eggs in one basket, not a very smart strategy," Lord Hill said.
"I know sometimes there is a sort of shorthand over here, which is well, you know, the Germans are kind of in charge so all you have got to do is square Mrs Merkel, it'll be fine. It doesn't work like that."
Asked if Mrs Merkel believed she was in charge, Lord Hill said: "The whole German thing for a long time since the war is they have become more powerful but they are frightened of being in charge."
Lord Hill told MPs Britain will have no-one to blame any more when things go wrong after it severs ties with Brussels.
"We'll have no-one to blame any more. It's going to be us," he said.
"When things don't work out, we are not going to be able to have that easy cop out of, oh yeah well it's Brussels."