Labour has retained the seat of Middlesbrough following a parliamentary by-election triggered by the death of the town's MP.
Since then, UKIP's fortunes have improved and it recorded its best performance in a parliamentary by-election in Rotherham in December.
The critics point to a recent parliamentary by-election in a safe seat, which the UMP held by only the thinnest of threads.
It is expected that the parliamentary by-election will be held on the same day, with an official announcement likely soon from the Commons.
BBC: NEWS | UK | Wales | South East Wales | MP's widow to fight assembly seat
Waverley councillor Diane James, who sits as an independent member, stood for UKIP in the Eastleigh Parliamentary by-election in Southampton earlier this month.
And Mr Blair's mind may be focused on the issue by defeat in February 3rd's parliamentary by-election in Ceredigion, a rural Welsh constituency held by Plaid.
The far-right National Front also fared well in France , winning nearly 40% of the vote in the first round of a parliamentary by-election in the southern city of Toulon.
His victory is the first time an independent or smaller party candidate has won a parliamentary by-election from another party in Britain since March 1973, when Dick Taverne won the Lincoln by-election (taking it from Labour).
This will be only the fifth occasion since the 1945 general election when the Lib Dems, or their predecessors the Liberals, have defended a parliamentary seat in a by-election.
The minor parties' success follows upon a record score in the 2001 general election as well as a string of saved deposits in parliamentary by-elections.
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Stephen Doughty, who was elected MP for Cardiff South and Penarth in a by-election last November, has been appointed (unpaid) parliamentary private secretary to shadow Chief Secretary to the Treasury, Rachel Reeves.
Worries about Ukrainian press freedom emerged during the run-up to the country's parliamentary election in March, when one opposition newspaper folded after a boycott by state-owned printers, and the country's only decent television news programme was mysteriously taken off the air.
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