NSW's opposition leader has caved to party pressure and quit his post, becoming the second state Liberal leader to do so in three days.

After days of swirling speculation, Mark Speakman announced his resignation.

Two challengers - Vaucluse MP Kellie Sloane and former minister Alister Henskens - are gunning for his position, with a leadership ballot set to be held.

Mr Speakman confirmed his resignation at a media conference on Thursday evening, having earlier cancelled a round of media interviews as speculation of a looming spill intensified.

One Liberal MP, speaking to AAP on the condition of anonymity, earlier said replacing Mr Speakman was a necessary move.

"We want to win government and it's not about the individual, it's about the team," the MP said.

"It's nothing personal agains

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