Whitehall's culture of reliance on ‘hired guns' – specialist interim employees brought in to cover a lack of in-house expertise within departments - must end, an influential parliamentary spending watchdog has demanded.

An investigation by the Public Accounts Committee (PAC) into 'off-payroll' arrangements stated more than 2,400 central government contractors were invoicing Whitehall employers using service companies – a practice arousing suspicions of complicity in tax avoidance.