Christopher Howarth is a senior Political Analyst at the think tank Open Europe. Prior to Open Europe he worked as a Conservative Foreign Affairs Adviser and senior researcher to a Shadow Europe Minister.

Imagine you woke up in a state where the head of the civil service was elected – but not by you. Imagine a state where the top governmental positions were settled in deals in meetings to which your elected representatives were not invited. Imagine that this system had been introduced without your approval. Well, you may soon be living in it if Jean-Claude Juncker becomes President of the European Commission.

So what should David Cameron do? His options are limited; the UK lost the veto on this appointment under the terms of the Nice Treaty in 2001. He can vote against, but cannot prevent himself being outvoted.

This is a major problem on two levels. First, by appointing Juncker EU member states have conceded the precedent that the European Parliament is now responsible for selecting the Commission President. This will politicise the Commission, and make it subject to perennial Brussels political deals between MEP factions. Juncker’s route to power has been paved by a series of such contradictory deals cut firstly with the Christian Democrat EPP; then the Socialist S&D; then, reportedly, the Socialist Prime Minister of Italy and French President – and allegedly the German mass circulation Bild newspaper. Needless to say, this bears no relation to the results of the recent European Elections and is a straightforward power grab. It is a cession of power not authorised or even discussed in the UK Parliament.

Beyond the principle and the person, Juncker’s appointment presents a strategic headache for David Cameron and his Europe policy. The assumed policy is to provide enough tangible evidence that the EU can reform to allow Cameron to advocate an ‘In’ vote in his promised 2017 referendum. In doing so, he has bet the farm (or the UK’s EU membership) on his belief that other member states, notably Germany, will wish to bail him out. Juncker’s appointment is a clear message that he cannot always rely on his fellow leaders to see him through when they come under their own domestic pressure.

So what should Cameron do? He could take being outvoted on the chin, hope for some consolation prize and pray that, next time, EU leaders will help him to deliver change. This is a risky approach. An alternative would be to send a direct message to his fellow leaders that he is not just in favour of EU reform but also believes that it is fundamental to the UK’s continued membership. Cameron could say that if the EU continues in the manner of Juncker’s appointment he will have no choice but to advocate an Out vote.

This would be interpreted as a threat, and be greeted by a wall of hostility in Brussels – but it would have the benefit of being true. It is not an idle threat. Cameron’s plan to base his referendum on the potential for EU reform was the right one, and one from which he cannot back down. Nor can he back the UK’s membership come what may. If he tried to pull the Harold Wilson trick of presenting a few concessions as a major triumph, he will be found out. After over 40 years of EU membership, a cynical British public will not be fooled. Remembering that Cameron was unable to block Juncker will not help in this regard. Cameron has to succeed in EU reform if he is to advocate an ‘in’ vote – it is time others in the EU began to realise that and act accordingly, or it may be Out by default.