London, Dec 12 (IANS): UK Prime Minister Boris Johnson on Thursday became the first leader of a major political party in Britain as he cast his ballot in one of the country's most crucial and decisive general election.

Johnson walked with his dog Dilyn, the rescue puppy he shares with girlfriend Carrie Symonds, to the polling station at the Methodist Central Hall next to Westminster Abbey, the Daily Mail reported.

Symonds however, did not accompany Johnson to the centre on biggest day of his political life.

Ahead of his vote, Johnson tweeted: "Today is our chance to get Brexit done. Vote Conservative."

Polling stations in 650 constituencies across England, Wales, Scotland and Northern Ireland opened at 7 a.m. (local time). After the polls close at 10 p.m., counting will begin straight away. Most results are due to be announced in the early hours of Friday morning.

Meanwhile, opposition Labour leader Jeremy Corbyn was also expected to vote early in his Islington North constituency.

Corbyn also wrote on social media: "Vote Labour today to save our NHS, to bring about real change and create a country that works for the many, not the few,"

Millions of voters face inclement weather with torrential rain and ice predicted across vast swathes of the country.

If a party wins in 326 constituencies it will have gained a majority.

A major YouGov poll on Tuesday predicted a 28-seat Conservative majority - the largest since 1987 - but pollsters said the situation was so volatile that Britain could face another hung Parliament.

Thursday's polls are the UK's third in less than five years and also the first winter election to take place in December since 1923.