The Prince of Wales's private estate is to be scrutinised by the Public Accounts Committee (PAC) as new figures show his funding from the taxpayer fell by almost 50%.

The Duchy of Cornwall, which provides heirs to the throne with a private income, will be examined by the body which has already looked at the tax affairs of Starbucks, Google and Amazon.

Charles's annual review showed the heir to the throne's funding from the taxpayer fell by 47% during the last financial year from £2.1 million to £1.1m.

The fall was in large part due to a reduction in travel costs as the overseas realms – countries where the Queen is head of state – footed the bill when he visited the nations.

Spending on official travel paid for through the sovereign grant – the new funding system which has replaced the civil list – and grants-in-aid fell during 2012/13 from £1.3m to £644,000.

Charles's income from the Duchy of Cornwall – a portfolio of land, property and investments – increased by 4% to reach a record level of £19m.

The Prince's tax bill fell slightly by £70,000 to £4.426m, a drop of 1.5%.

William Nye, Charles's principal private secretary, said: "Naturally we're happy to appear before the Public Accounts Committee, if they would like to see us."

He added: "The Duchy estate provides an income for the heir to the throne, there are some special rules that apply to it.

"The Prince of Wales gets the income from the Duchy but he doesn't have access to the capital, that's always been the case."