LONDON (AFP) - Prime Minister Gordon Brown faced his first poll test Thursday since a leadership crisis last month, as electors in eastern England voted in a by-election that could deal him a new ballot blow. Browns Labour party is fighting to keep the parliamentary seat of Norwich North from the main opposition Conservatives, who are leading national polls ahead of a general election due within a year. A strong showing for the Tories could reignite questions over Browns leadership, a month after he suffered a crisis of confidence among his own party following historic defeats in local and European elections. The vote will likely reflect continuing public anger at a scandal over lawmakers parliamentary expenses, which has rocked British politics and sparked Thursdays by-election. Incumbent Labour MP Ian Gibson, who held a majority of 5,500, was ejected following an internal party inquiry into revelations that he claimed thousands of pounds on a London flat before selling it at cut price to his daughter. The expenses row has hit all the main parties in Westminster, but Labour in power since 1997 has suffered the most. It has been languishing at least 10 points behind the Conservatives in the opinion polls for months, struggling with a perception that it has run out of steam. The recession meanwhile has dealt a personal blow to Brown because of his previous job as finance minister under former premier Tony Blair. Some commentators expect voters in Norwich North to punish all the main parties and back fringe groups such as the British National Party (BNP), which won its first two seats in the European Parliament in May, and the Green party. Brown sought to play down any defeat ahead of the vote, telling reporters at his monthly news conference on Wednesday that the by-election was being held in unique circumstances given Britains deep recession and the expenses row. I hope people who are Labour voters will come out and vote Labour but I think people do understand the uniqueness of this by-election resulting from the parliamentary events that came before, he said. Labours campaign took a hit earlier this week when its candidate was taken to hospital with suspected swine flu. Chris Ostrowski is now at home but is unlikely to take any part in campaigning Thursday or attend the count. Conservative leader David Cameron has previously made a series of high-profile visits to the constituency, which has been Labour since 1997 but was Tory for 14 years before that. An ICM survey for the News of the World newspaper at the weekend put the Conservatives on 34 percent in Norwich North, with Labour on 30 percent, the centrist Liberal Democrats on 15 percent and the Green party on 14 percent. Polls opened at 7:00am (0600 GMT) and close at 10:00pm. Results are not due until about midday on Friday.