The NHS links pre-dated David Cameron hiring Mr Crosby however it is the second time the Prime Minister has had to defend his controversial election strategist over claims of lobbying.
Mr Cameron has insisted that Mr Crosby had not intervened in policy decisions, but has repeatedly refused to answer questions about the extent of his conversations with the lobbyist.
The Prime Minister has come under sustained pressure to say whether Mr Crosby, whose lobbying company has also worked for tobacco giant Philip Morris, had spoken to him about shelving the plan for cigarettes to be sold in plain packaging.
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