The Supreme Court today slammed Delhi Police for its "half-hearted" probe into the cash-for-vote scam and asked it to take the investigations to its logical conclusion and submit a final report within three weeks.

A bench of justices Aftab Alam and R M Lodha also regretted that a middleman of the "cheapest kind" was allowed to derail Parliamentary proceedings.

"It is a half-hearted attempt by you (Delhi police). You must take it to the logical conclusion," the bench said after perusing the preliminary report of Delhi Police which had claimed that no political leader was involved in the 2008 scam.

Declining to grant 40 days time sought by Delhi Police, the court asked it to submit a final report within three weeks.

The apex court regretted that a middleman was allowed to interfere with Parliamentary proceedings.

"It is so disgusting that a middle man of the cheapest kind had been allowed to interfere with Parliamentary proceedings and he had succeeded," the bench observed.

The apex court hoped that Delhi Police will do a fair and free investigation into the alleged unfortunate episode.

"We are sure that the Delhi Police can investigate in a fair and free manner. They are as good as any other investigating agency and will follow the law in letter and spirit," the bench told Additional Solicitor General Haren Rawal, appearing for the probe agency.

Delhi Police had yesterday filed before the apex court its status report on the probe into the scam in which it has arrested Suhail Hindustani and Sanjeev Saxena and quizzed MPs Amar Singh, Rewati Raman Singh and Ashok Argal.

The report was submitted to the court in a sealed cover.

Delhi Police had swung into action after the apex court had on July 15 expressed unhappiness over the "callous" approach to the probe.

Saxena, an alleged aide of Amar Singh, was the first to be arrested on July 17 for allegedly trying to bribe BJP MPs during UPA government's trust vote on July 22, 2008.

The second arrest was that of Hindustani, who is alleged to have acted as a liaison between Amar Singh and the BJP MPs, who were allegedly bribed during the trust vote.

The police had virtually given a clean chit to Congress and Samajwadi Party on July 21 when it told a trial court here that none from the two parties had contacted Hindustani, the alleged "master orchestrator" of the conspiracy to bribe BJP MPs to vote in favour of Manmohan Singh government in the trust vote.

Police had also told the court that former Bihar Governor Buta Singh's son Arvinder Singh was approached by Hindustani for contacting Congress leaders for striking a deal while allegedly hatching a conspiracy to bribe BJP MPs during the confidence motion.

Amar Singh, former Samajwadi Party General Secretary and Rajya Sabha member, was interrogated for about three hours by Delhi Police on July 22.

The police had also interrogated Samajwadi Party MP Rewati Raman Singh on July 25 and BJP MP Ashok Argal on July 26 in connection with the scam.