Voting for the two by-elections in Ealing Southall - better known as Little India - and Sedgefield began on Thursday morning with police investigating complaints that trends in postal ballots for the former had been leaked on the Internet.
The by-election in Ealing Southall, in west London, was triggered by the death of Labour's Piara Singh Khabra on June 19. The Sedgefield constituency in Durham county goes to the polls following the resignation of Tony Blair as prime minister and MP.
The Sedgefield seat is considered ultra-safe for the Labour Party, but Conservative and Liberal Democrats have poured in large resources to challenge Labour in Ealing Southall, where the "robust" campaigning had echoes of a colourful Indian election.
The two by-elections are the first since Gordon Brown took over as prime minister. A Labour victory in both will contribute to ongoing discussions within the party of capitalising on the high ratings enjoyed by Brown to call an early general election.
The three leading candidates in Ealing Southall are Virendra Sharma (Labour), Tony Lit (Conservative) and Nigel Bakhai (Liberal Democrat).
Hours before voting began in Ealing Southall, the Metropolitan Police launched an investigation following complaints that results and trends of postal ballots had been leaked on the Internet by a 'Conservative source'.
A posting on a Daily Telegraph website - subsequently withdrawn - claimed that the Tories were neck and neck with Labour and the Liberal Democrats trailing in third place, about five points behind.
It is possible for campaign headquarters to get a sense of the results of postal voting, but it is a breach of electoral law to communicate this information because it can influence voters going to the polls. Anyone found guilty of leaking such information can face six months in prison.
The Telegraph site quoted a source in the Conservative campaign saying that, based on the process of verifying the postal ballots, the result was likely to be close. All political parties are allowed to have representatives overseeing the validation process, but any release of an indication as to how the votes are going for each party is prohibited.
Schedule 6 of the amendments passed in 2000 to the 1983 Representation of the People Act states: "No person shall, in the case of an election to which this section applies, publish before the poll is closed any statement relating to the way in which voters have voted at the election where that statement is (or might reasonably be taken to be) based on information given by voters after they have voted."
A Telegraph Media Group spokesperson said: "A blog was filed at about 6 pm. It was on the site for a short period of time until it was pointed out that it might be in breach of electoral law and it was removed instantly this was pointed out."
A Conservative spokesperson said: "We haven't seen this blog so it's difficult to comment. The fact that the blog has now been removed speaks for itself. Our agent in Ealing Southall hasn't published any such information or spoken to the Daily Telegraph. We suspect that this is mischief making by our opponents."