The White House has stepped up its resistance to the impeachment inquiry into Donald Trump, as top officials including Mike Pence told the House committees leading the Ukraine probe that they would not provide information to investigators.

Th vice-president told the Democratically-controlled committees through a White House lawyer that the impeachment inquiry was not valid because the full House of Representatives had not voted to open an inquiry. His argument comes a week after the White House counsel told Democrats that their Ukraine investigation “violates the constitution”.

Earlier on Tuesday Rudy Giuliani, the personal lawyer to Mr Trump who is under intense scrutiny over his role in the  Ukrainegate scandal, refused to comply with a subpoena from the congressional committees investigating the US president.