Lord Ashcroft owns a 37.16 per cent of parent company Watford Leisure Plc
Lord Ashcroft, Watford's majority shareholder, has lent the club a further £500,000.
A statement from parent company Watford Leisure Plc said the money will "assist with the working capital requirements of the business".
Ashcroft will cancel his loans in return for a share in the £10.1m worth of bonds to be created later this year.
It takes the deputy chairman of the Conservative Party's total lendings to over £6.5m.
The bond issue, given the go-ahead by shareholders during an extraordinary general meeting in May, will also be used to cancel the loans from director David Fransen (£2.05m) and former chairman Graham Simpson (£592,000).
The Watford Leisure Plc statement added: "The amount outstanding under the secured loan is now, in aggregate, approximately £6.55 million (including accrued interest).
"Security is by way of a guarantee and debenture over the Vicarage Road Stadium ranking behind certain other pre-existing secured creditors.
"The secured loan is intended to be cancelled as part of the Company's proposed issue of secured bonds with detachable warrants in due course."
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