The two Scottish knights who are trying to parachute themselves into the HBOS boardroom were accused yesterday of egotism and arrogance and of hatching an irresponsible plan that could destroy the bank.

The vitriolic attack against Sir Peter Burt and Sir George Mathewson was made by Derek Simpson, joint general secretary of Unite, Britain's biggest union.

Mr Simpson said that the two men were irresponsible for trying to derail the planned takeover of HBOS by Lloyds TSB, a move that he said could destabilise the banking system.

He said: “We have serious concerns that the extreme arrogance of these two individuals will lead to the nightmare scenario in which HBOS collapses.”

Mr Simpson questioned the motives of the men, noting that Sir George, while he was running Royal Bank of Scotland, oversaw the loss of 18,000 jobs after the NatWest takeover.

Sir Peter, as the architect of the original merger of Bank of Scotland with Halifax, must bear some responsibility for the mess HBOS had got into, Mr Simpson said.

The two bankers hit back, accusing Unite of inconsistency. “It was only a week ago that Unite was criticising the Lloyds takeover and the risk of job losses,” their spokesman said.

Mr Simpson's attack also triggered a furious response from Alex Neil, an SNP MSP. “This is an incredibly bizarre response from someone whose interests should be protecting the jobs of HBOS and Lloyds TSB employees at all costs,” Mr Neil said.

“If the takeover is allowed to go ahead, up to 40,000 HBOS and Lloyds TSB employees could face job losses. They should be Mr Simpson's primary concern.” Unite has about 20,000 members in branches and call centres across the two banks.

Last week Lloyds intensified concerns that job losses would be heavy when it raised its forecast of merger cost savings from £1billion a year to £1.5billion.

Gordon Brown dismissed calls for the takeover to be rejected, arguing that Lloyds was the only serious bidder for HBOS. The Prime Minister said that it was the only realistic option.

A rescue bid orchestrated by Jim Spowart, the former HBOS executive, has failed to bear fruit, so far. However, Bank of China apparently is the mystery bidder with which he is speaking.

The Burt/Mathewson plan envisages no immediate buyer; rather, it calls for a breathing space in which HBOS would continue to operate on a standalone basis.

Sir Peter and Sir George have called on Lord Stevenson of Coddenham and Andy Hornby, the HBOS chairman and chief executive respectively, to hand over control to themselves and to abort the Lloyds deal, which they argue penalises HBOS shareholders unfairly.

Lloyds shares fell by 9 per cent to 177.4p yesterday, and HBOS shares were down by 8 per cent at 99.2p.

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