Leading Republican lawmakers have called for a US justice department investigation into whether McKinsey violated federal law by failing to disclose potential conflicts of interest between its work in China and for the Pentagon.

In a letter to US attorney-general Merrick Garland, seen by the Financial Times, the head of the House select committee on the Chinese Communist party and two US senators said McKinsey appeared to have breached government contracting rules and misled Congress.

The demand for an investigation raises political pressure on the consulting firm, whose extensive work for the US military has been in the crosshairs of Republican lawmakers who argue that McKinsey’s simultaneous work in China represents a risk to US national security, something the firm denies.