The prosecutor was asked to turn to parliament by a Vilnius court, which is hearing the Labour Party's fraudulent bookkeeping case.
The three MPs and the party's former accountant Marina Liutkevičienė along with the party as a legal entity are charged with fraud.
On the same grounds, previous parliament had stripped Uspaskich and Gapšys off their legal immunity in December 2008. After they were elected to the new Seimas in October, a sanction from this parliament is necessary to proceed with the case.
A Vilnius court has been hearing the case since April 2008. The Labour Party and the related individuals were earlier charged with submitting incorrect income, profit, or asset data to state institutions with the goal of evading taxes but the charges were revised on 26 October and redefined as fraud.
Prosecutors have said earlier the Labour Party's financial documentation for the 2004-2006 period failed to include about 25 million litas (EUR 7.3 million) in income and about 23 million litas in spending related with property, commitments, and structural changes, and also failed to pay taxes of around 4 million litas.
The State Tax Inspectorate has also filed a suit in the case, as it has not received more than 3 million litas in taxes and fees, as well as by the Vilnius branch of the state-run social insurance fund Sodra over damages caused by refusal to pay more than 855,000 litas in insurance fees.
Uspaskich strongly denies all charges.