Britain's prime minister David Cameron
'David Cameron's default setting for relationships with most continental leaders is neglect.' Photograph: Pascal Rossignol/Reuters

David Cameron's European diplomacy looks disastrous under scrutiny. Apparently, it is just as bad when Westminster's attention is elsewhere. The spotlight has moved away from the mishandling of Jean-Claude Juncker's nomination as European commission president, but the cack-handedness continues behind closed doors. A diplomatic source tells me that the message briefed from the Foreign Office to other EU member states in the aftermath of last week's Brussels summit is that Britain feels mistreated and that compensation should be forthcoming. The tone from London is querulous – a veiled threat along the lines of: "You shafted us, now you help us, otherwise how can we stay in your club?" Recipients of this ultimatum were stunned. They had expected conciliation.

Politicians and ambassadors from fellow member states know that Cameron has a problem with his party's fanatical Eurosceptics and are not unsympathetic. Every prime minister has to balance the demands of a domestic audience, often fomented by partisan newspapers, with the practical need to compromise in Brussels. Indeed, it was Angela Merkel's own experience of just such pressures that led her to accept Juncker as the least worst option. The surprising thing is that Downing Street was surprised at the defeat. More astonishing still is that whispers of German betrayal wafted out of the back door of No 10 in disgruntled briefings; as if no one in Berlin reads British newspapers. Was the idea of a political leader putting domestic considerations ahead of European business really so hard for a UK prime minister to get his head around?

It isn't the substance of British objections to Juncker that other EU member states found hard to fathom. As was widely reported, many agreed in private with Cameron's reservations. The problem was the failure to play the European game by its rules. It is normal for one member state to object to a commission nominee, but the way to express that view is to propose someone else. Cameron tried to block Juncker with no one else in mind, as if everyone else should scurry off and find a suitable replacement to suit His Highness's tastes.

A second blunder was to think that the whole thing could be sewn up between London and Berlin. The fact that Juncker hails from Luxembourg was treated in Britain as a sign of his second-rate status. But Europe has many small states and they are sensitive to signs of bullying by mightier neighbours. It doesn't pay in European alliance-building to be beastly to the Benelux. And, of course, there is the remarkable forfeiture of relationships in the east. The Tories have sabotaged friendships in Bucharest and Warsaw by endorsing a Ukip view of Romanians and Poles in the UK as criminals and benefit-gobblers.

Above all, however, the problem appears to be Cameron's long-standing aversion to detail. The prime minister has great confidence in his capacity to perform under exam conditions; to let others get on with the boring technical stuff and put on a bravura display at the last minute if problems arise. He doesn't do patient slog. But that is the stuff of which European partnerships are made. It isn't enough to roll out the red carpet for Merkel, fix up a date for her to have tea with the Queen and then wait for the favours to come in. It isn't enough to ignore European affairs except when British tabloids take an interest or backbench rebellion looms. And it isn't enough to only start swotting up on the issues when the Eurostar is pulling out of St Pancras.

There is every reason to suppose Cameron will now revert to that pattern. He survived the summit. His party's appetite for anti-Brussels defiance is temporarily sated. The media caravan has moved on. Westminster's attention is elsewhere. But the European diplomacy doesn't stop. Cameron must now find a suitable candidate to serve as a commissioner, and he must secure him or her a good portfolio with plenty of economic clout. Before the Juncker debacle the name being circulated was Andrew Lansley – a man famously lacking in diplomatic finesse and who, it is widely rumoured, was promised the gig by Cameron as part of a deal for accepting cabinet demotion in 2012. Fellow Europeans look at this prospect in disbelief. Is Cameron really going to try to persuade Juncker to give a plum commissioner job to this also-ran loser?

One final point, apparently lost on No 10, is that the rest of the EU has things on its mind other than placating British Eurosceptics. Thinking up concessions to keep the UK on board is on the agenda but not ahead of finalising the financial reforms necessary to put the eurozone on a more stable footing, or measures to address chronic continent-wide youth unemployment. But there isn't any sign Cameron wants to engage on that level. He knows what he needs to get out of Brussels but he has no idea how to go about getting it. He lurches from insouciance to demand to defiance. His default setting for relationships with most continental leaders is neglect. And while they understand why it is so, they don't have to like it. After a while, systematic neglect looks like abuse.