Labour leader Ed Miliband has described Alex Salmond as an "undercover lobbyist" for media tycoon Rupert Murdoch.
Mr Miliband said the First Minister had questions to answer about his links to the News Corporation chairman. His comments come the day after Mr Salmond faced accusations that he was prepared to lobby UK Culture Secretary Jeremy Hunt regarding the proposed takeover of BSkyB.
Mr Salmond insisted his interest in the deal was linked to employment. But Mr Miliband, who was campaigning with his party in Glasgow, said: "I think the revelations about Mr Salmond are shocking revelations.
"Just like the Prime Minister has very serious questions to answer now about his relationship with Rupert Murdoch, so does the First Minister. If, as he claims, this was all part of a concerted attempt to bring jobs to Scotland, why wasn't he open about his support for the BSkyB bid?
"Why wasn't he open about the fact he was set to lobby Jeremy Hunt in favour of the BSkyB bid? If he had nothing to hide, why did he hide it?
"What he actually did was acted as an undercover lobbyist for Rupert Murdoch. I don't think that's what people expect of the First Minister of Scotland.
"I think they want a First Minister who will stand up for ordinary people in Scotland, not the rich and powerful.
"I look forward to Alex Salmond answering the questions he's got to answer and the account he's got to give of himself in the coming weeks. I don't think the bluster and the bluffery that we saw yesterday is going to get him through."
Mr Miliband also referred to links between Mr Salmond and Mr Murdoch after revelations about the phone-hacking scandal.
Mr Miliband added: "He's the guy who, after Millie Dowler, what did he do? He didn't call for a judicial inquiry, he didn't say stop the BSkyB bid, what did he say? He invited Rupert Murdoch to tea."