tories accuse ed miliband of stooping to a ` shameful ' new low in campaign .
labour leader attacked the prime minister 's 2011 intervention in libya .
said the refugee deaths were the result of the aftermath of the intervention .
a briefing went further claiming they were ` direct result ' of pm 's decisions .
comes after eu leaders agreed package of measures to tackle the crisis .
mr cameron agreed to send a royal navy warship to the region within days .