Gordon Brown will travel late to Lisbon tomorrow to sign the new European Union Reform Treaty – but he will do so without the other 26 leaders.

The Prime Minister will miss the official ceremony but append his name to the treaty on Britain’s behalf whenever he arrives, prompting accusations that he does not want to be seen doing the deed.

William Hague, the Shadow Foreign Secretary, said that Mr Brown did not “have the guts” to do it in public.

Mr Brown is to be questioned by the Commons Liaison Committee of select committee chiefs for up to 2½ hours tomorrow. The session will end at about 11.30am.

Although Lisbon is in the same time zone as London, Mr Brown was never going to get to the signing celebrations in time. He may arrive towards the end of lunch and will sign the treaty then. Officials said that Mr Brown’s personal signing ceremony would take place in the same room as the group ceremony, and cameras would be present.

David Miliband, the Foreign Secretary, will be present during the official signing at noon in Lisbon’s historic Jerónimos Monastery, which will take place before the cameras.

Mr Brown will also miss speeches by José Manuel Barroso, the President of the European Commission, Hans-Gert Pöttering, President of the European Parliament, and José Sócrates, the Portuguese Prime Minister, who holds the presidency of the European Council.

Mr Brown will also be absent from the official “family photograph” of the heads of government who have signed the reform treaty. There were quips at Westminster that he could “do a Purnell” and have his photograph added to the official one. James Purnell, the Culture Secretary, was criticised when his image was added later to a photograph of MPs who had attended a hospital opening, suggesting that he had been there.

Mr Barroso urged Mr Brown last night to stop being a “reluctant partner” in Europe. He has seen Mr Brown once – in London – since he became Prime Minister in June. Mr Barroso, speaking to The Times, said: “We need the commitment of all the major partners. Nicolas Sarkozy is there, putting in initiatives, and I welcome that. I would prefer to have Britain doing the same.”

Mr Brown’s spokesman explained how the diary clash had arisen. “There had been some uncertainty about the exact date when the treaty would be signed. The Liaison Committee was agreed for December 13. We have done everything we can to accommodate the PM’s travel plans to Lisbon and the Liaison Committee agreed to move forward their meeting from 10am to 9am.”

The spokesman said that Mr Brown’s presence for the ceremony was “not a particularly significant issue” as previous EU treaties had been signed by foreign secretaries on behalf of the UK. The Lisbon Treaty will bear the names of heads of government and the foreign ministers of all 27 EU states. The day after the signing, Mr Brown is due to attend a one-day EU summit in Brussels.

Mr Hague said: “Some people say Gordon Brown’s problems are that he isn’t decisive and he lacks political courage. He couldn’t have done more to confirm that than this ridiculous fudge. He’s dithered over it for a week and now he’s decided that he’ll sign this treaty but he doesn’t have the guts to do it in public.

“His excuses fool no one. He must stop treating people like fools. If he backs the renamed EU constitution so much that he’s ready to break his manifesto promise, he should at least have the courage to be photographed doing it.

“If he’s ashamed of signing this treaty, then why doesn’t he honour his election promise and let the British people have their say?”

Green campaigners have attacked the decision to hold one half of the summit in Lisbon and the other in Brussels. Portugal, which holds the EU presidency, insisted that the signing was in Lisbon so it could be known as the Lisbon Treaty. Belgian officials countered that under the rules all routine summits had to be in Brussels.

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