Campaigners backing Britain remaining in the EU will be able to outspend Out supporters by more than £14 million, a Conservative grandee has claimed.

Former cabinet minister Lord Forsyth of Drumlean argued political parties must be prevented from spending money on the referendum campaign to prevent the pro-EU movement being accused of having "bought" the result thanks to "big business and big money".

He said the Government's EU Referendum Bill allows, according to current sums, the campaign for Britain to remain in the EU to spend £25.5 million compared with £11 million for those supporting Brexit.

Peers heard the two designated campaigns on either side of the EU argument will receive £7 million which can then be topped up by political parties.

But the Conservative Party decision to remain neutral means the pro-EU campaign will benefit from increased spending, Lord Forsyth said.

Former Conservative chancellor Norman Lamont backed Lord Forsyth's call for equal spending between the two campaigns.

Moving an amendment to the Bill at committee stage, Lord Forsyth told peers: "Whatever the outcome of the referendum it's important people feel the Government did not abuse its position, whatever its position turns out to be, and that the campaign was conducted in a fair and balanced way."

He said he believes the Electoral Commission's job is to ensure "fair and balanced" conduct in such votes, adding the purpose of designated campaigns on each side of the argument with spending limits is to ensure fairness.

The Tory said: "But what do I find? I find that the Government has brought into the Bill the ability of the political parties to spend money in addition to the designated campaigns.

"So in the case of the designated 'In' campaign they can spend £7 million, in the case of the designated 'Out' campaign they can spend £7 million - fair enough.

"But then on the inside, the Labour Party can spend £7 million, the Liberal Democrats can spend £3 million, the Greens can spend £700,000 and the CBI and other organisations can spend £700,000.

"Now the Conservatives have said that they will remain neutral and that is to very considerable credit to the Conservative board for taking that decision."

He went on: "If you add that up as it stands on the Bill, those who wish us to remain inside the European Union will be able to spend £25.5 million and those people who wish us to leave - together with the political parties because Ukip will be able to spend £4 million - will be able to spend £11 million.

"That seems to me to be a tad unbalanced."

He noted all parties have people with differing views on the issue, adding that is why only two campaigns are needed.

Lord Forsyth said: "At the end of the day, as we know from American elections and elsewhere, ability to spend money can have a marked effect on the result and the last thing we want is if the campaign to stay in is successful is that people argue that the election result was bought and that it was unfair and led by big business and big money."

For Labour, shadow spokesman Lord Collins of Highbury questioned what happened during the 2015 general election.

He said: "Who had the most money? Do we call that into question? Who paid for it? I know exactly how much the unions gave the Labour Party and I know how that money was collected."

Lord Collins asked if it was unfair for hedge funds to enable the Tories to "outspend every other party".

Earlier, he said political parties have the right to campaign on certain issues that they "feel united about" and for which voters have supported them on.

Tory Lord Lamont of Lerwick said of the spending allowances for political parties: "I find it very difficult to understand how this can be justified.

"I don't see the necessity of it. It would have been extremely simple if the Government insists on having a cap on spending in the campaign to have it the same for both sides."