Flavour-changing neutral current decays such as c→ul+l- are highly suppressed in the Standard Model (SM), but may be enhanced by New Physics. For D0→μ+μ-, the SM decay rate is dominated by long distance contributions but is still a few order of magnitudes below the current experimental limit. In decays such as D+→π+μ+μ-, measuring the differential branching ratio as a function of the μ+μ- invariant mass is a sensitive probe for New Physics contributions. We present the latest results of searches for rare charm decays at LHCb.