A novel proton imaging technique was applied which allows a continuous temporal record of electric fields within a time window of several nanoseconds. This "proton streak deflectometry" was used to investigate transient electric fields of intense (∼ 1017 W cm2) laser irradiated foils. We found out that these fields with an absolute peak of up to 108 Vm extend over millimeter lateral extension and decay at nanosecond duration. Hence, they last much longer than the (approximately picosecond) laser excitation and extend much beyond the laser irradiation focus.