New figures from the Rural Payments Agency show it has spent 505,782 since 2005 on entertainment, with the costs said to largely relate to refreshments during meetings.
The RPA also handed out more than 16m in overtime payments in the past five years – with the bill averaging at well over 3m a year since 2005.
The statistics were revealed following a series of parliamentary questions tabled by the former shadow environment spokes-man for the Liberal Democrats, Tim Farron and follows a series of highly critical reports into the RPA's inefficiencies.
The RPA spent nearly 2m on bonus payments to staff, despite the widespread problems within the agency regarding their work.
Mr Farron said: "These figures show once and for all the wasteful legacy of the Rural Payments Agency under the previous Labour government.
"Farmers up and down the country will find it hard to stomach the fact the RPA were throwing away nearly 1,000 a week on entertainment at a time when many farmers were left counting the pennies as a result of the RPA's ineptitude.
"Questions must also be asked as to exactly what sort of 'advice' the RPA were getting from their consultants. Given that over five years they wasted nearly 130m, it's safe to say it wasn't advice on taxpayer value for money."
Jim Paice, the Coalition government's Agriculture Minister who has taken responsibility for reforming the RPA over the next few years, provided Mr Farron with the answers to his questions.
Mr Paice has agreed to stake his Ministerial career on revamping the agency, including installing a new management team.
Richard Judge, formerly chief executive of the Centre for Environment, Fisheries and Aquaculture Science (Cefas), has taken over as chief executive on an interim basis.
In the past 12 months two reviews, one by the National Audit Office and one by its parent department Defra, have strongly criticised the lack of value for money and performance of the RPA.
Claims of inefficiencies and excessive spending by Government departments and quangos were last week reinforced with the accounts for the Department for Communities and Local Government which showed civil servants spent thousands on luxury hotels, M&S lunches, away days and staff massages last year. Staff in the Home and Communities Agency spent 5,003 at four-star spa retreats.
Matthew Elliott from the Tax Payers' Alliance, referred to the RPA entertainment bill as "needless expenditure".
Mr Elliott said: "Farmers and taxpayers alike will despair that the consistently disastrous RPA has wasted so much money on refreshments. It is inevitable that some staff will have to work some extra hours, but this is a staggering overtime bill."
A spokeswoman for the RPA said: "'Entertainment' costs have reduced by 50 per cent over the past year and RPA continues to look at cost savings across the business.
"These costs for catering include those incurred across all RPA sites and from our regular meetings and briefings with key industry groups involved in the 40 plus schemes delivered by RPA."