During the first half of 2013, the United Kingdom joined France in pressing the EU to lift its embargo on the sale of arms and other military equipment to Syria in an effort to support the opposition to the regime of Bashar al-Assad. In late August Cameron sought to intervene more directly in the Syrian Civil War by backing a proposed U.S.-led strike against chemical-weapons installations following a poison gas attack on suburbs of Damascus that allegedly had been launched by Syrian government forces. He recalled Parliament from its summer break for an emergency debate in order to secure approval for British participation in the retaliatory military intervention. The Labour Party and a significant number of Conservative and Liberal Democratic MPs, however, were reluctant to support action, as was the general public.

As part of an attempt to modify his proposal so as to overcome the doubts of MPs, Cameron recast the vote on August 29 so that it was focused on the principle of military action and guaranteed that MPs would be granted a second vote, some days later, before British forces went into action. This meant that Britain could not participate in a U.S.-led attack according to the original timetable. Even so, 30 Conservative and 9 Liberal Democratic MPs voted against the government, and similar numbers abstained. Ultimately, the government proposal was defeated 285–272. It was the first time since 1855 (during the Crimean War) that any British government had been defeated in a House of Commons vote on military action overseas. Cameron announced immediately that he accepted the result, that he would not seek to have the vote overturned at a later stage, and that the country would not take part in military action against Syria.

In October Andrew Parker, the head of the government intelligence agency MI5, indirectly accused The Guardian newspaper of jeopardizing the U.K.’s security following that newspaper’s reporting of documents disclosed by Edward Snowden, who had worked for the U.S. CIA and National Security Agency (NSA), that indicated that the British surveillance agency, the Government Communications Headquarters (GCHQ), had a far greater capacity to eavesdrop than had been publicly acknowledged. A fierce debate erupted between those (such as The Guardian and many MPs in all parties) who argued for tighter, more-effective controls on the work of GCHQ and those (such as Parker and some newspapers and MPs) who felt that GCHQ needed as much freedom as possible to monitor potential terrorists and others who threatened British interests. Cameron joined Parker in condemning the leaks, maintaining that the activities of the GCHQ were lawful and necessary for the protection of the British people.

Relations between the press and Parliament were also strained by the continuing repercussions of the 2011 phone-hacking scandal. The 2012 public inquiry led by Lord Justice Leveson at Cameron’s behest recommended a new, tougher system of press regulation, and dozens were arrested during a series of investigations regarding phone hacking and bribery of public officials. In October 2013 seven people linked to News of the World faced trial for phone hacking, and five others pleaded guilty to avoid trial. That same month the Privy Council granted a royal charter (which had been agreed to in March by Cameron, Clegg, and the Labour Party’s leader, Ed Miliband) that established a new watchdog system that would give press regulators statutory powers. In June 2014 Coulson, Cameron’s former communications chief, was found guilty of conspiring to hack phones, and in July he was sentenced to 18 months in prison.

Although Cameron continued to promise an “in or out” referendum on the EU, the Conservatives had largely ceded the issue of Euroskepticism to UKIP. In May 2014 UKIP made huge gains in local elections and finished first in EU parliamentary elections, leading some Conservatives to suggest an alliance with UKIP. Cameron rejected the notion, stating that UKIP leader Nigel Farage wished to “destroy the Conservative Party, not work in tandem with it.” Cameron experienced a reversal within the EU in July 2014 when Jean-Claude Juncker, a candidate whom he had strenuously opposed, was elected president of the European Commission. That same day Cameron announced the most significant cabinet reshuffle of his administration, appointing a group of ministers who reflected a markedly Euroskeptic outlook. Dozens of ministers were sacked or had their portfolios changed. Among those leaving government or accepting reduced responsibilities were foreign secretary William Hague, education secretary Michael Gove, and Ken Clarke, a minister without portfolio who had long been the most consistent pro-EU voice within the Conservative front bench.