The UK's National Cyber Security Center (NCSC, part of GCHQ) has written to the British political parties to warn about "the potential for hostile action against the UK political system." Without confirming that the main threat is from Russia, the letter makes it clear that the primary threat is considered to be that country.
Article Link: http://feedproxy.google.com/~r/Securityweek/~3/IVe8LOCqWoQ/uk-intelligence-agency-warns-russian-political-hacking-capabilities