Unhappy with the Congress proposal on ministerial berths, the Dravida Munnettra Kazhagam on Thursday decided to extend outside support to the United Progressive Alliance government at the Centre.
"The Congress formula is not acceptable to us," DMK leader T R Baalu told reporters after talks between the two sides.
Baalu announced the breakdown of talks after Prime Minister Manmohan Singh called up DMK chief M Karunanidhi, who conveyed his rejection of the Congress proposal.
DMK had been demanding seven ministerial berths, including three cabinet, while Congress was ready to concede only six.
Baalu said there had been no formula for government formation in 2004.
The DMK's executive council is going to meet in Chennai on Friday to discuss its future course of action.
However, Congress spokesperson Janardhan Dwivedi said that the negotiations with the Congress were not over. DMK's demand for status quo and a little more than that in portfolios was not acceptable to the Congress, he added.