Juliet Stevenson is leading calls for the Government to do more to reunite child asylum seekers in the EU with their families in the UK.
The actress has launched a petition with Citizens UK to demand that the Government steps in to help children who are separated from their families while trying to claim asylum.
The charity said 17-year-old asylum seeker Muhammed Hassan died last week in a traffic accident 14 miles from David Cameron's Oxfordshire home as he tried to reach his uncle in Manchester.
A spokeswoman said: "He had a legal right to come to the UK to be with his family while his asylum claim was processed, but no safe method of travelling here from Calais, where he had been living in the squalid conditions of The Jungle.
"He had travelled from Iraq, fleeing the violence of Islamic State."
The Dublin III Treaty, which governs EU asylum applications, says refugees must claim asylum in the first safe country they enter.
However, Dublin III also says refugees with a nuclear family in a third country should claim asylum on entry to the EU and can then formally request that the third country "takes charge" of their application.
Citizens UK says that in practice this rarely happens and no children made a successful "take charge" application from France to Britain from the time the system was established in 2013 to last month.
After a legal battle, the first children from The Jungle camp were allowed into the UK to be reunited with their families last month but Citizens UK estimates there are 150 more children in Calais who could come to Britain under the rules.
Stevenson said: "These families have a full legal and moral right to be reunited.
"The Prime Minister must take personal responsibility for these tragedies which have now arrived at his doorstep.
"He must step in and ensure that all refugee children with family members in the UK across Europe are identified and supported to reunite with their loved ones with all possible urgency.
"Government must act and ensure clear information is given to these children in a language they understand, legal and psychiatric assessments and support are provided, family tracing and age verification processes are observed where required, and the family reunion process is completed with all possible haste."