ING, one of Europe's largest banks, said its central assumption was Brexit would be delayed, with a 40 percent chance of a national election in the United Kingdom.

ING economist James Smith said his central assumption was that Britain would end up with an election.

"It is very risky to go to the voters if there is a no-deal Brexit," Smith told. "A general election looks increasingly likely."

Parliament, he said, was likely to force a vote of no confidence on Johnson's government and then would try to force a delay to Brexit.

"There's a 40 percent probability of a general election coupled with an Article 50 extension," Smith said, referring to the notification Britain would leave the EU. He raised the probability of a no-deal Brexit to 25 percent from 20 percent.

The bank said sterling could fall to 95 pence per euro this quarter and that the British economy would feel the pressure too.