John Swinney is facing a wave of damaging speculation over his future as leader of the Scottish National Party.

Recent media reports have suggested that the SNP chief could face a "stalking horse" challenge this autumn.

The news follows a poor nationalist performance in the May 1 elections to the Holyrood parliament.

After a bruising campaign, the party lost eight seats and took just 24 per cent of constituency votes.

Alex Neil, the Central Scotland MSP who stood against Swinney for the party's leadership three years ago, is said to have described the result as "disastrous".

His comments echo the wave of discontent among party representatives which forced Ieuan Wyn Jones to step down as leader of Plaid Cymru.

But Swinney appears set to stand firm against any attempt to oust him as leader.

The most likely challenger is Bob Scott, a Glasgow party activist who is said to be currently gauging support for a bid.

Scott is said to be angered by a perceived failure to push the party's independence platform.

He could seek to topple Swinney at the party's autumn conference.

However, the SNP leader has vowed to step up the fight for separation from the rest of the UK.

At the party's national council meeting in Perth at the weekend, he accepted that the nationalists had so far failed to convince Scottish voters of the benefits of independence.

But he said the SNP had "won the argument over how Scotland moves on to independence".

"The great challenge for our party now is to win the argument over why Scotland should move on to independence," he added.

He also refuted claims that he had not emphasised the independence platform.

Swinney said the policy had been put centre stage because "it couldn't be ducked".