He made the comments as the Labour Party in Wales launched its own manifesto.
The findings are from the latest Welsh Political Barometer poll and put Labour on 44%, up from the 35%.
In the last general election in 2015, Labour lost 40 seats in Scotland.
Scottish Labour will put opposition to a second independence vote at the front and centre of its manifesto.
Under Mr Clegg the Lib Dems were criticised for their U-turn on a pledge to abolish tuition fees after going into coalition with the Conservatives.
Phil Wilson last year called on Jeremy Corbyn to resign as party leader in the aftermath of the EU referendum.
The shadow education secretary’s comments come after the PM revealed her fantasy guest list for dinner.
The deadline to sign up to vote in the General Election passes at 11.59pm on Monday.
One in 10 (10%) of respondents thought Labour will become the majority party in Parliament.