@ Anonymous Coward
'Oh, except Blair gave us the Parliament Act '
Actually though they're the sort of law that would give him wet dreams, Blair got beat to it - twice, once in 1911 and once in 1949. However New Labour have abused the two Parliament Acts and used them far more than any other government.
Labour is also committed to further reducing the power of the Lords should it be re-elected, further tipping powers towards the executive in the Commons.
As for extending the life of a Parliament...
The Parliament Act 1911 set the term to a maximum of five years, but that is not absolute. A series of acts passed in the Second World War extended Parliament for a maximum of ten years on the grounds that an election would be a distraction and potentially divisive during a crisis.
So a government could introduce a bill that struck down all or part of the Parliament Act 1911 and simply declare a new maximum term (we've had maximum terms of both three and seven years in the past); or they could try and declare a situation so serious that an election wasn't in the country's best interests.
I'd hope that there are still enough members of the Parliamentary Labour Party that neither of those are a goer.