The meeting was held on a day Singh is holding consultations with UPA allies on the Lokpal issue, the first such exercise after the fiasco over FDI in retail.
Finance Minister Pranab Mukherjee, Home Minister P Chidambaram, Defence Minister A K Antony and Congress president's political secretary Ahamed Patel were present at the Congress core group meeting in which the Lokpal issue was discussed, sources said.
Singh's meeting with the UPA leaders is expected to project a united face of the ruling alliance on the issue of Lokpal at a time when it was under attack from opposition parties and Anna Hazare for coming out with a "weak" bill.
The consultations will be held a day ahead of an all-party meeting convened by the Prime Minister on the ticklish issue.
Last week, the government had to put the decision on allowing 51 per cent FDI in multi-brand retail on hold following key allies Trinamool Congress and DMK expressing opposition to it and demanding its rollback.
The Lokpal bill is expected to come up for consideration in the Lok Sabha on December 20, two days ahead of the conclusion of the current session of Parliament.