The Uttar Pradesh police's alleged snooping on former Prime Minister V P Singh, who is in the midst of a campaign against the state's ruling Samajwadi Party ahead of the Assembly polls, on Tuesday snowballed into a major row.

The Centre expressed concern and the state government announced an inquiry.

Union Minister of State for Home Sriprakash Jaiswal said that the three detained Ghaziabad policemen said they were tailing V P Singh in Delhi on Sunday to find out whether he was going to Uttar Pradesh.

But there is more to the issue than what the police claim, he said.

Jaiswal met the former prime minister, who had complained to the Centre that he was being tailed, and inquired about the incident which took place on Sunday.

During the meeting, Jaiswal also discussed a possible alliance between Jan Morcha led by Singh and Congress, party sources said.

Uttar Pradesh Chief Minister Mulayam Singh Yadav told reporters in Lucknow that his government would conduct an inquiry into the incident. "I came to know about it from the media. V P Singh is a respected leader and a former prime minister of the country. The matter will be investigated", he said.