Rev Mervyn Gibson told the News Letter last night he had a message for anyone who had not yet signed the declaration.
“I am calling on you to add your names to the thousands who have already signed,” he said.
“We must send a clear message to Europe – the protocol as is must go.”
The declaration remains open for signatures at reception at Schomberg House on the Cregagh Road in east Belfast until 5.30pm today.
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However, people can also still sign the online declaration at www.goli.org.uk/declaration until midnight tonight.
Talks remain ongoing between the UK government and the European Union aimed at resolving issues surrounding the protocol.
Brexit Minister Lord Frost said last week a “significant” gap remained between the UK and the EU.
While some progress on medicines was welcomed, the UK team was understood to be disappointed that there has been little in the way of progress on the flow of goods between Britain and Northern Ireland while governance and subsidy control remain points of contention.
On Saturday unionists visited around 250 Orange halls across Northern Ireland to sign the declaration against the protocol.
Harold Henning, deputy grand master of the Orange Order, said at this stage they were leaving it for politicians to “sort out”, but suggested rallies could be called in future if deemed necessary.