Ruling UPA's key ally DMK on Wednesday issued a veiled threat of pulling out of the alliance on the issue of the "atrocious" petrol price hike, saying the party had never hesitated to do so earlier respecting people's sentiments.

"The DMK is in the coalition. But (being in) alliance is different. It is our duty to voice concern against policies that will affect the people," DMK chief M Karunanidhi told a large gathering of party supporters to protest against the central government for hiking petrol prices and the state government for increasing bus fares and milk prices.

The 88-year-old DMK patriarch said his party had walked out of alliances, "whether it be the BJP (led NDA) or while being in the VP Singh cabinet."

"We have never hesitated to raise voice of opposition whenever the basic principles were hurt and if we cannot solve it by being an ally, we have not hesitated to come out and uphold those principles," he said even as his remarks were loudly cheered by partymen.

Describing the hike as "atrocious", Karunanidhi said not just opposition parties or UPA constituents but even Congress leader and defence minister A K Antony had expressed dissent over the petrol price hike, saying it was unacceptable.

"Prime minister Manmohan Singh should take cognisance of this and offer relief to the common man," he said.