PKR is claiming having acquired "solid testimony" supporting allegations that defecting MPs were offered RM2 million and multi-million ringgit government contracts.

Party de facto chief Anwar Ibrahim said the testimony provided "explosive" evidence of political corruption practised by Umno's leadership and their agents.

"We are still waiting for their (defectors) reactions before releasing the information publicly.

"We will make a public expose in the near future," he said in a statement today, in the lead up to the party national congress in Kota Bharu tomorrow.

A total of five PKR members of parliament have bailed out of the opposition coalition this year, with four jumping off the boat and the other sacked.

The most recent defection was by Wangsa Maju MP Wee Choo Keong, who quit on May 14 over what he claimed was the poor handling by the Selangor government of corruption involving state-owned mining company Kuala Semesta Sdn Bhd.

The others are Bagan Serai MP Mohsin Fadzli Samsuri who quit on March 3, Nibong Tebal MP Tan Tee Beng (March 1) and Bayan Baru MP Zahrain Mohd Hashim (Feb 12).

Kulim Bandar Baru MP Zulkifli Nordin was sacked on March 6 for openly criticising and lodging a police report against his Pakatan Rakyat colleagues.

Anwar had apologised earlier this year for selecting bad candidates to contest under PKR's flag in the 2008 general election, saying he was "sad that I asked you to vote for these people - I apologise. Now I have been stabbed in the back".

He, however, implied in an interview with Malaysiakini earlier this week that PKR elected representatives were being "bought over".