May won 318 out of parliament's 650 seats in 2017, forcing her to rely on a small Northern Irish party to govern. Johnson lost that majority last week after Conservative Party defections and the decision to kick out 21 of his lawmakers who rebelled over Brexit.
"We are looking at picking up roughly 295-300 seats," Jason Stein, who was an adviser to former works and pensions minister Amber Rudd who quit the government on Saturday, told Sky News, citing private polling for Johnson's 10 Downing Street office.
"Number 10 themselves privately will tell you that it will be a tough election. They are not expecting this to be the land of milk and honey."He said the Conservatives were going to lose seats in Scotland, London and southwest England.