The British newspaper 'The Guardian' reports that Muammar Gaddafi warned Tony Blair in 2011 that his removal from the Libyan leadership would open a space for al-Qaida to seize control of the country and even launch an invasion of Europe. Based on this information, I do believe that Blair's decision to remove Gaddafi from Libyan Leadership opened space for an invasion of Europe by al-Qaida.
Tony Blair's decision to remove Qaddafi was very short sighted and did contribute to the rise of al-Qaida, and other jihadist groups, who want to invade, and are invading Europe even as we speak. Under Qadaffi, the citizens of Libya appeared, for all intents and purposes, to be happy with his leadership. Libya happened to be one of the few countries that didn't have a central bank and the "Powers that Be" couldn't have that. The other two countries that didn't have a central bank were Iraq and Syria, and we know how Iraq ended up. Now the target is on Syria.
Tony Blair's decision to intervene in another state likely created some enemies; there were most likely people upset with the idea that a European leader had the power to alter the government of Libya. That anger alone may have provided momentum for extremist groups such as al-Qaida to carry out activity in Europe, and also in other parts of the world.
Ever since the overthrow of Muammar Gaddafi in Libya, sanctioned by Tony Blair, the country has been in a state of disarray and turmoil. Terrorist organizations like al Qaeda and ISIS have had a free run of the country, operating terror camps and controlling large swathes of territory. With the chaos that exists in Libya today in the absence of a strong central leadership, it has become extremely easy for groups like al Qaeda to plot terror attacks against the West, and Europe in particular, considering the physical proximity. A situation like this, or the Benghazi incident for that matter, would never have arisen in the days of Gaddafi.