On average, the prince attended nearly two engagements a day
Taxpayers funded the work of the Prince of Wales to the tune of £3m last year - an annual rise of almost a quarter, according to Clarence House accounts.
A 48% rise in spending on air and rail travel, which grew to £1.71m, accounted for much of the hike in official costs.
He travelled more than 50,000 miles to attend 658 official engagements during his 60th birthday year.
Charles's private income increased by just 1% to £16.4m during the last financial year.
He also paid less tax, with his bill falling almost 10% from more than £3.4m to just under £3.1m.
The prince's non-official expenditure fell by 23% to £1.7m, with the drop being attributed in part to his decision to holiday in the UK last year.
Campaign group Republic - which is pressing for an elected head of state - has called on the government to stop funding his work.
This is a double whammy for the taxpayer - less tax and more subsidies.
Graham Smith, Republic
But the prince's supporters say his foreign trips - which are requested by the UK government - are key to maintaining relations and promoting trade.
His senior aide, Sir Michael Peat, said the rise in official travel costs was due to two long-haul trips to the Far East and South America.
"It's easy to underestimate the importance and success of these tours," Sir Michael said, adding that Charles had been mindful of the economic downturn.
"It's a recession and we have to say that we've looked at all costs very carefully," he said.
Prince defended over spending rise
"We are by no means immune to it. We are always reviewing all costs the whole time."
The annual review suggests the prince helped to raise £130m in support of his 20 core charities.
A keen environmental campaigner, Prince Charles also presided over a 7% cut in carbon emissions at Clarence House during the year to April.
Fossil fuel use was reduced by 15%, the report said.
In the year to April, the surplus generated by the Duchy of Cornwall - the landed estate given to the heir to the throne - increased by only £185,000.
This private income had risen by 7% during the previous year.
Clarence House said Charles spent "well over half" of this £16.4m after-tax income in support of official and charitable activities.
However, taxpayers supplement this work through government grant-in-aid payments, which help to fund official travel, property and communications.
Some of the increased cost was due foreign travel
The last financial year saw these payments jump 23.5% from £2.45m to £3.03m, while Charles's official expenditure rose by nearly a fifth from to £10.45m to £12.5m.
The accounts reveal £6.2m went on staff salaries, £65,000 on his gardens and more than £500,000 on official entertaining and receptions.
Author Ingrid Seward, who has written extensively about the Royal Family, told the BBC that Charles offered "value for money" and was "no burden" on the taxpayer.
"When Prince Charles goes on foreign trips it's not [simply] because he wants to, it's because he's invited by foreign countries and it must be paid for because he's a great ambassador," she said.
However, Republic spokesman Graham Smith said: "This is a double whammy for the taxpayer - less tax and more subsidies while the government is having to make swingeing cuts to public services."
Calling for full disclosure of the prince's expenses, he added: "After months of public anger over MPs' expenses it is now time for Charles to come clean. He appears to claim butlers and personal dressers as business costs, thereby saving him a small fortune in tax."
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.