A senior UK minister has warned that Islamic State terror group is plotting mass casualty chemical attacks against Britain. <br/><br/>Minister in charge of security Ben Wallace said Islamic State had used chemical weapons in Syria and Iraq and intelligence chiefs believe it has an aspiration to use them in Britain. <br/><br/>Wallace warned that as IS has been driven out of its strongholds in the Middle East, returning terrorists will pose a growing threat to Britain. About 800 Britons went to fight in Syria and just under half have returned. <br/>