You are unable to transfer from Tier 2 ICT to Tier 2 General whilst in the UK. You will need to return to your home country and make a new application from there.
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In short, there is a cooling off period of 12 months which would prevent you from submitting an application during that period.
A foreigner who is in the UK on a TIER 2 visa and who either leaves the UK at the end of their assignment or whose visa expires without the possibility of renewal, must wait at least 12 months to obtain a new TIER 2 visa. Referred to as the “Cooling Off Period,” this 12 month window is calculated from either the date of the foreign national’s last departure from the UK or the expiration date of their visa. Traditionally, this rule has put a significant restriction on companies who need foreign workers in the UK for short assignments as foreign employees must wait at least 12 months to return for another assignment of any length.
I note that you are an established member of staff. As this is the case, you can switch to a Tier 2 general if you are applying to change sponsor, i.e. take new employment.
Sorry for the confusion, I misread the original information.
Long Term Staff are also sometimes referred to as established staff.