As Burning Our Money states, "25 million voters are now directly dependent on the state for all or part of their incomes". Following the link in BOM's post, immediately after the quote, leads one to this graph, which is startling in what it shows.
On the basis that 25 million is almost half the population of the UK, what the Labour Party has done is in effect 'gerrymandering'. Gerrymandering may be used to achieve desired electoral results for a particular party, or may be used to help or hinder a particular group of constituent, such as a political, racial, linguistic, religious or class group.
Do read both articles - very illuminating indeed.
Afterthought: Errm, is gerrymandering not a criminal offence?