T-Mobile has already lined up a successor to Munro, with Unilever Bestfoods senior category marketing manager Philip Chapman set to replace him in January.
A T-Mobile spokeswoman said that it was discussing other career opportunities with Munro.
Munro joined T-Mobile in 1994 and was promoted to marketing director two years ago. He had previously headed its consumer insight, research, analysis and pricing strategy.
His resignation follows accusations that T-Mobile's UK brand advertising has lost its way. The German firm is reviewing its global brand strategy, which will include the closure of its Hammersmith office, as first revealed by Marketing.
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